Hao-Wu Lin

Interfacial losses at the perovskite/C60 and C60/metal contacts limit inverted perovskite solar cell performance. Here, we introduce a vacuum-evaporated molecule with giant spontaneous orientation polarization, 6F-2PI, for simultaneously tailoring both interfaces. Incorporating 6F-2PI increases the work function of perovskite, reducing the conduction band offset at the perovskite/C60 interface, which facilitates electron extraction. Concurrently, its phthalimide moieties passivate defect states, suppressing nonradiative recombination, as evidenced by a 0.03 eV recovery in quasi-Fermi level splitting. At the C60/metal interface, 6F-2PI also delivers efficient charge extraction, improved interfacial contact, and thermal resilience. Moreover, its hydrophobic fluorinated units prevent moisture ingress. Consequently, this dual-interface modulation boosts PCE from 18.5% to 22.5% with exceptional device stability, retaining over 90% of its initial efficiency after 2000 h under ambient conditions. Furthermore, this framework exhibits universal compatibility across both vacuum-deposited and solution-processed devices and simplifies processing for mass production.

Overcoming the long‐standing trade‐off between efficiency and radiative rate in metal‐free phosphorescence remains a central challenge in molecular photophysics and is pivotal for the next‐generation optoelectronic technologies. Here, we demonstrate that tuning the strength of anion–π ⁺ interactions in pyridinium‐based contact ion pairs (CIPs) enables exceptionally fast room‐temperature phosphorescence (RTP) spanning 540 to 605 nm and, with radiative rates reaching 5.2×10 ⁵ s ⁻¹ , places this crystalline material among the fastest known organic phosphors. By systematically tuning electron deficiency, steric confinement, and CIP organization through mono‐ and dicarboxyester‐functionalized pyridinium iodides, we achieved unusually short and highly polarized I ⁻ –π ⁺ tunable contacts that approach 3.50 Å. Structural analysis reveals not only tightly bound, sandwich‐like, and columnar‐organized ion pairs but also unexpected dynamic behavior, including reversible, thermally activated anion drift in the solid state. Collectively, these solid state features engender strongly coupled iodide → π ⁺ charge‐transfer states with enhanced spin–orbit coupling, thereby promoting ultrafast intersystem crossing. Spectroscopic and theoretical studies identify an intensity‐borrowing mechanism within the charge‐transfer manifold that underlies the accelerated phosphorescence and/or thermally stimulated delayed phosphorescence. The resulting materials show promising X‐ray scintillation performance. Our work establishes anion–π ⁺ engineering as a general and previously underexploited strategy for achieving high‐rate, metal‐free phosphorescence.

Overcoming the long‐standing trade‐off between efficiency and radiative rate in metal‐free phosphorescence remains a central challenge in molecular photophysics and is pivotal for the next‐generation optoelectronic technologies. Here, we demonstrate that tuning the strength of anion–π ⁺ interactions in pyridinium‐based contact ion pairs (CIPs) enables exceptionally fast room‐temperature phosphorescence (RTP) spanning 540 to 605 nm and, with radiative rates reaching 5.2×10 ⁵ s ⁻¹ , places this crystalline material among the fastest known organic phosphors. By systematically tuning electron deficiency, steric confinement, and CIP organization through mono‐ and dicarboxyester‐functionalized pyridinium iodides, we achieved unusually short and highly polarized I ⁻ –π ⁺ tunable contacts that approach 3.50 Å. Structural analysis reveals not only tightly bound, sandwich‐like, and columnar‐organized ion pairs but also unexpected dynamic behavior, including reversible, thermally activated anion drift in the solid state. Collectively, these solid state features engender strongly coupled iodide → π ⁺ charge‐transfer states with enhanced spin–orbit coupling, thereby promoting ultrafast intersystem crossing. Spectroscopic and theoretical studies identify an intensity‐borrowing mechanism within the charge‐transfer manifold that underlies the accelerated phosphorescence and/or thermally stimulated delayed phosphorescence. The resulting materials show promising X‐ray scintillation performance. Our work establishes anion–π ⁺ engineering as a general and previously underexploited strategy for achieving high‐rate, metal‐free phosphorescence.

Increasing the volume of halide perovskite nanocrystals (NCs) is generally accompanied by lower photoluminescence quantum yield (PLQY). Here, we overcame this trade‐off with giant (25 nm) rhombicuboctahedral CsPbI ₃ NCs that retain an exceptional PLQY of 87%. Their distinct size and morphology were induced by using phenacyl iodide as a novel precursor and subsequently characterized by x‐ray diffraction and transmission electron microscopy. In these giant NCs, the non‐radiative Auger process is suppressed, giving rise to a high biexciton PLQY of 55%, while a high single‐photon purity up to 95% was achieved using a time‐gating method. Benefiting from their enlarged volume, these NCs achieve one of the largest reported absorption cross‐sections of 5.3 × 10 ⁻¹³ cm ² , along with emission tunable to the near‐infrared region (>700 nm) and a prolonged room‐temperature lifetime of 465 ns—nearly an order of magnitude longer than conventional NCs. In contrast, at cryogenic temperatures, these enlarged NCs exhibit narrow and ultrafast emission ( τ = 467 ps) arising from the coherent coupling of dipoles within a single NC, which induces a giant oscillator strength and leads to single‐photon superradiance. These results position the unique rhombicuboctahedral, giant CsPbI ₃ NCs as novel near‐infrared emitters and promising candidates for high‐speed quantum photon sources.

Simultaneously achieving high sensitivity and ultrafast response is a challenge for photodetectors, a bottleneck further compounded by the environmental toxicity of lead‐based halide perovskite photodetectors. Herein, we overcome these limitations via a lead‐free, quasi‐2D germanium‐based halide perovskite, PEA ₂ MA ₃ Ge ₄ I ₁₃ . Distinguished by its non‐centrosymmetric structure, this material exhibits robust ferroelectricity, pyroelectricity, and second‐order nonlinear optical susceptibility. By coupling the pyroelectric effect and photovoltaic effect, we successfully decouple the conventional sensitivity‐speed trade‐off, achieving a very high specific detectivity of 6.3 × 10 ¹⁴ Jones alongside a remarkable response time in ns scale. The practical viability of these devices is demonstrated through advanced applications in tens of centimeter‐level (1 ns light travelling time) light detection and ranging (LiDAR) and fast visible light communication (VLC). This work establishes a compelling strategy for realizing next‐generation, environmentally benign, and high‐performance optoelectronics.

Chiral sulfur quantum dots synthesized using cysteine as a “chiral surfactant” achieved a photoluminescence quantum yield >80% and good circularly polarized luminescence under 375 nm excitation.

Achieving strong light-matter interaction to manipulate emission requires integrating colloidal perovskite quantum dots (PQDs) with plasmonic nanocavities, yet this integration is challenged by their vulnerability to polar solvents. We successfully synthesized highly emissive, solvent-resistant CsPbI ₃ PQDs and integrated them into nanoparticle-on-mirror structures. This integration enabled a 435-fold reduction in emission lifetime and a 250-fold increase in total emission intensity. Key results include a very short radiative lifetime below 12 picoseconds and a record-high single-photon emission rate exceeding 2.3 × 10 ⁹ counts per second at room temperature. Notably, we also observed nonblinking single-photon emission with high purity arising from nanocavity-enhanced radiative electron-hole recombination. Finite-difference time-domain simulations confirmed ultrasmall mode volumes of ~3 × 10 ⁻⁵ (λ/ n ) ³ , effectively enhancing spontaneous emission via the Purcell effect. These ultrabright and nonblinking properties highlight the strong potential of this platform for future quantum technology applications.